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FAILED: patch "[PATCH] kcmp: Support selection of SYS_kcmp without" failed to apply to 4.9-stable tree

PATCH [email protected] 1 participant 1 message Mar 1, 2021

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Stable branch DRM drivers VFS DRM misc +2 more subsystems
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The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From bfe3911a91047557eb0e620f95a370aee6a248c7 Mon Sep 17 00:00:00 2001
From: Chris Wilson <[email protected]>
Date: Fri, 5 Feb 2021 22:00:12 +0000
Subject: [PATCH] kcmp: Support selection of SYS_kcmp without
CHECKPOINT_RESTORE

Userspace has discovered the functionality offered by SYS_kcmp and has started to depend upon it. In particular, Mesa uses SYS_kcmp for os_same_file_description() in order to identify when two fd (e.g. device or dmabuf) point to the same struct file. Since they depend on it for core functionality, lift SYS_kcmp out of the non-default CONFIG_CHECKPOINT_RESTORE into the selectable syscall category.

Rasmus Villemoes also pointed out that systemd uses SYS_kcmp to deduplicate the per-service file descriptor store.

Note that some distributions such as Ubuntu are already enabling CHECKPOINT_RESTORE in their configs and so, by extension, SYS_kcmp.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/3046

Signed-off-by Chris Wilson <[email protected]>
Cc Kees Cook <[email protected]>
Cc Andy Lutomirski <[email protected]>
Cc Will Drewry <[email protected]>
Cc Andrew Morton <[email protected]>
Cc Dave Airlie <[email protected]>
Cc Daniel Vetter <[email protected]>
Cc Lucas Stach <[email protected]>
Cc Rasmus Villemoes <[email protected]>
Cc Cyrill Gorcunov <[email protected]>
Cc [email protected]
Acked-by Daniel Vetter <[email protected]> # DRM depends on kcmp
Acked-by Rasmus Villemoes <[email protected]> # systemd uses kcmp
Reviewed-by Cyrill Gorcunov <[email protected]>
Reviewed-by Kees Cook <[email protected]>
Acked-by Thomas Zimmermann <[email protected]>
Signed-off-by Daniel Vetter <[email protected]>
Link https://patchwork.freedesktop.org/patch/msgid/[email protected]
drivers/gpu/drm/Kconfig +3 -0
index 0973f408d75f..af6c6d214d91 100644
@@ -15,6 +15,9 @@ menuconfig DRM
 	select I2C_ALGOBIT
 	select DMA_SHARED_BUFFER
 	select SYNC_FILE
+# gallium uses SYS_kcmp for os_same_file_description() to de-duplicate
+# device and dmabuf fd. Let's make sure that is available for our userspace.
+	select KCMP
 	help
 	  Kernel-level support for the Direct Rendering Infrastructure (DRI)
 	  introduced in XFree86 4.0. If you say Y here, you need to select
fs/eventpoll.c +2 -2
index a829af074eb5..3196474cbe24 100644
@@ -979,7 +979,7 @@ static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
 	return epir;
 }
 
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#ifdef CONFIG_KCMP
 static struct epitem *ep_find_tfd(struct eventpoll *ep, int tfd, unsigned long toff)
 {
 	struct rb_node *rbp;

@@ -1021,7 +1021,7 @@ struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd,
 
 	return file_raw;
 }
-#endif /* CONFIG_CHECKPOINT_RESTORE */
+#endif /* CONFIG_KCMP */
 
 /**
  * Adds a new entry to the tail of the list in a lockless way, i.e.
include/linux/eventpoll.h +1 -1
index 0350393465d4..593322c946e6 100644
@@ -18,7 +18,7 @@ struct file;
 
 #ifdef CONFIG_EPOLL
 
-#ifdef CONFIG_CHECKPOINT_RESTORE
+#ifdef CONFIG_KCMP
 struct file *get_epoll_tfile_raw_ptr(struct file *file, int tfd, unsigned long toff);
 #endif
init/Kconfig +11 -0
index 29ad68325028..b7d3c6a12196 100644
@@ -1193,6 +1193,7 @@ endif # NAMESPACES
 config CHECKPOINT_RESTORE
 	bool "Checkpoint/restore support"
 	select PROC_CHILDREN
+	select KCMP
 	default n
 	help
 	  Enables additional kernel features in a sake of checkpoint/restore.

@@ -1736,6 +1737,16 @@ config ARCH_HAS_MEMBARRIER_CALLBACKS
 config ARCH_HAS_MEMBARRIER_SYNC_CORE
 	bool
 
+config KCMP
+	bool "Enable kcmp() system call" if EXPERT
+	help
+	  Enable the kernel resource comparison system call. It provides
+	  user-space with the ability to compare two processes to see if they
+	  share a common resource, such as a file descriptor or even virtual
+	  memory space.
+
+	  If unsure, say N.
+
 config RSEQ
 	bool "Enable rseq() system call" if EXPERT
 	default y
kernel/Makefile +1 -1
index aa7368c7eabf..320f1f3941b7 100644
@@ -51,7 +51,7 @@ obj-y += livepatch/
 obj-y += dma/
 obj-y += entry/
 
-obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
+obj-$(CONFIG_KCMP) += kcmp.o
 obj-$(CONFIG_FREEZER) += freezer.o
 obj-$(CONFIG_PROFILING) += profile.o
 obj-$(CONFIG_STACKTRACE) += stacktrace.o
tools/testing/selftests/seccomp/seccomp_bpf.c +1 -1
index 26c72f2b61b1..1b6c7d33c4ff 100644
@@ -315,7 +315,7 @@ TEST(kcmp)
 	ret = __filecmp(getpid(), getpid(), 1, 1);
 	EXPECT_EQ(ret, 0);
 	if (ret != 0 && errno == ENOSYS)
-		SKIP(return, "Kernel does not support kcmp() (missing CONFIG_CHECKPOINT_RESTORE?)");
+		SKIP(return, "Kernel does not support kcmp() (missing CONFIG_KCMP?)");
 }
 
 TEST(mode_strict_support)